Interest rates on short-term Treasury bills rose in Monday's auction, and rates on three-month bills climbed to their highest level since late February.

The Treasury Department auctioned $30 billion in three-month bills at a discount rate of 0.095 percent, up from 0.08 percent last week. Another $28 billion in six-month bills sold at a discount rate of 0.145 percent, up from 0.13 percent last week.

The three-month rate was the highest since these bills averaged 0.115 percent on Feb. 27. The six-month rate was the highest since these bills averaged 0.15 percent on April 9.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,997.60 while a six-month bill sold for $9,992.67. That equals an annualized rate of 0.096 percent for the three-month bills and 0.147 percent for the six-month bills.

Separately, the Federal Reserve said Monday that the average yield for one-year Treasury bills, a popular index for making changes in adjustable rate mortgages, was unchanged at 0.18 percent last week and the week before.